1. Field of the Invention
The invention is directed to an at least partially rotating and axially percussive hand-held machine tool such as a multipurpose hammer having an impact mechanism and a slip clutch arranged at the guide tube of the pneumatic spring.
2. Description of the Prior Art
Particularly in percussive rotary drilling in reinforced concrete, the drilling head can become hooked on embedded reinforcing iron resulting in a rotation of the housing. For this reason, a safety clutch arranged between the driving motor and the tool receptacle reliably interrupts the flow of force in case of tool blockage.
In a safety clutch constructed as a slip clutch, the flow of force is interrupted as soon as a permissible maximum torque is exceeded. When the slip clutch is additionally constructed as a frictionally locking slip clutch, torque fluctuations that can help to unhook the drilling head are generated in case of tool blockage with repeated engagement of the flow of force. These torque fluctuations must be absorbed substantially by the user.
Further, particularly in high-power hand-held machine tools having a power rating of more than 1000 Watts, another safety clutch is designed as an electronically controlled magnetic clutch and is arranged in the flow of force before the transmission gear unit and behind the rapidly rotating motor, where substantially smaller coupling torques occur.
In a rotating and axially percussive hand-held machine tool according to DE 4304899, a first, lockable slip clutch is arranged on the guide tube and a second slip clutch is arranged in the flow of force in front of the transmission gear unit.
In a rotating and axially percussive hand-held machine tool according to EP 1207018, a safety clutch is constructed as an electronically controlled magnetic clutch and is arranged in the flow of force in front of the transmission gear unit directly behind the rapidly rotating motor.
In a rotating and axially percussive hand-held machine tool according to DE3804414, a slip clutch surrounding the rotatable guide tube has a driving sleeve that is driven in rotation by a bevel pinion and has a female bevel sleeve which is biased axially by a pressure spring, and by which balls that are radially displaceable in rotary driving holes of the driving sleeve are pressed into matching ball depressions of the guide tube for rotary driving.
According to DE10033100, a rotating and axially percussive hand-held machine tool has an impact mechanism with a rotating guide tube in which a percussion piston is driven in an axially percussive manner by a pneumatic spring. A slip clutch, which encloses the guide tube and is provided axially with cams, has a driving sleeve that is driven in rotation by a bevel pinion and a driven sleeve. The driving sleeve and driven sleeve are axially biased relative to one another under pressure by a spring. The driven sleeve is connected to the guide tube so as to be axially displaceable and fixed with respect to rotation relative to it.
Further, U.S. Pat. No. 2,907,240 and GB963533 disclose rotating and tangentially percussive impact wrenches with a slip clutch which is constructed as a tangential impact mechanism and provided axially with cams, and comprises a rotationally driven solid cylindrical control shaft having V-shaped grooves in which balls engage, where each ball is arranged in an associated triangular pocket of a driving part that is displaceable in an axially spring-biased manner.